Hitherto, the inspection of a defection, a detriment or the like on a side wall surface of a hole has been conducted on an image of the side wall surface photographed by an omnidirectional imaging device such as an endoscope or the like. Generally, the photographed annular image is converted into a panoramic development image for the inspection.
In the conversion, if the optical axis of the omnidirectional imaging device deviates from the central axis of the hole, it is necessary to conduct a correction process. As such correction process, there has been disclosed in Japanese Patent Laid-open No. 2000-331168 a technique which obtains the deviated amount between the optical axis of a video camera and the central axis of a tubular drain by conducting a data matching process as the video camera is used to photograph the inner surface of the tubular drain.